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Dateline: 03/08/00
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The ISP quantum dot: an Iron-Sulfur cluster. Structure determined by Iwata et. al. Image created with 32-bit RasWin PDB ID = 1BE3 | |
Quantum dots are objects so small that adding or removing a single electron represents a significant change. While the integration of quantum dots into computers threatens to make Pentium processors as obsolete as vacuum tubes, such objects are nothing new to biological systems. Take for instance the electron transport chain used by nearly every living organism for energy conversion. Numerous proteins in this chain, as well as some smaller organic electron carriers all act as quantum dots. The image above is a model of part of the Iron Sulfur Protein (ISP), which uses its Iron Sulfur cluster to shuttle electrons from one quantum dot (quinone) to the next (Cytochrome C1). As it does so, conformation changes throughout the multi-enzyme complex that it is a part of pump protons across a membrane resulting in a molecular battery. Single electron transfers abound in biological systems. Catalases are enzymes that use quantum dots to convert the damaging H2O2 into water. The photosynthetic machinery of plants use numerous quantum dots to absorb light and pass their energy and electrons to the complex "photosystems" that convert this energy into nanomechanical fuel, otherwise known as sugar. In the world of computer science, quantum dots are viewed from a different perspective than in biochemistry. While in biochemistry they are generally referred to as redox groups, chip designers refer to them as qubits[Collins]. Researchers such as Yasunobu Nakamura at the NEC Fundamental Research Laboratories in Tsukuba, Japan, have combined a superconducting phase with a quantum dot in an attempt to build a quantum computer. Such a computer would use qubits much as a modern computer uses bits. However, qubits may have an advantage over macroscale bits due to the quantum mechanical principle of superposition, or the ability to be in two states at once. This principle may allow a single qubit to be used in more than one computation simultaneously. Numerous quirks of quantum mechanics are being found to be advantageous to quantum computing. For instance, the "quantum mirage" discovered at IBM provides evidence that wires may not even be necessary in some nanoelectronic circuits.
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Keywords: quantum dots qubit nakamura single electron transport chain superposition quantum mechanics computer biomolecular nanotechnology biomimetic nanoelectronic circuits integration biological systems energy conversion protein organic carriers iron sulfur protein ISP quinone cytochrome C1 conformation pump transfer catalases photosynthesis photosysem nanomechanical fuel sugar redox group superconducting mirage IBM
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